1. Field
Some example embodiments relate to insulating sheets having a heterogeneous laminated structure, methods of manufacturing the same, and/or laminated structures and transistors including the laminated sheets, which may be used in various electrical devices.
2. Description of the Related Art
Graphene is a material composed of a single carbon atom layer having a two-dimensional planar structure, and since graphene has desirable mechanical and electrical characteristics, it has received much attention as a new high-performance electronic material. Since characteristics of graphene may significantly degrade according to its relation with respect to a substrate when the graphene is used in a real electronic device, there is a need to form a laminated structure on a substrate having insulating properties as well as an atomically flat surface in order to realize a device having desirable characteristics.
An appropriate material that may be used as a substrate for the laminated structure is hexagonal boron nitride (hereinafter, referred to as “h-BN”). h-BN is a material having a two-dimensional structure, in which the h-BN is composed of hexagonal arrays of boron atoms and nitrogen atoms, has electrical insulating properties due to a large bandgap of about 5.9 eV, and corresponds to a physically and mechanically stable material. Since an h-BN crystal has a hexagonal laminated structure similar to that of graphite, the h-BN crystal forms a very rigid bond and has lubricity. Also, an h-BN sheet is a covalently bonded material formed of elements with a low atomic number, in which the h-BN sheet has very high thermal conductivity, has very high stability at high temperatures because it does not have a melting point and sublimes at about 3000° C., has a resistance of about 105 Ω at a high temperature region above about 1000° C. due to very high electrical resistance, has high chemical stability due to very stable hexagonal bonding, and may induce weight reductions in components of aircrafts and spaceships because a true specific gravity thereof is about 2.26 which is a very low value among ceramics.
In order to use the h-BN sheet as a substrate for laminating graphene, there is a need to form an h-BN sheet having a large area as well as desirable surface characteristics.